The pleiotropic fibroblast growth factors (FGF) control a broad spectrum of cellular processes, including prostate development, function, and homeostasis, by activating the four highly homologous FGF receptor (FGFR) transmembrane tyrosine kinases. Aberrant expression and activation of the FGF signaling axis are often found associated with prostatic tumor development and progression. FRS2? is an adaptor protein linking the FGFR kinases to downstream signaling targets, which is differentially phosphorylated by the FGFR1 and FGFR2 kinases in prostate epithelial cells. FRS2? is dynamically expressed in developing prostates, which is associated with prostatic branching morphogenesis, androgen-induced regeneration, and tumorigenesis. The project is to test the hypothesis that FGFR isoform-specific activation of FRS2?-mediated signals play important roles in regulating proliferation and differentiation of precursor cells for prostatic epithelial cells during development and regeneration, and aberrant activation of FRS2?-mediated signaling contributes to prostatic tumorigenesis, which was formulated based on our recent findings. Efforts will be focused on using genetically engineered mouse as well as molecular biological, cell biological, and biochemical technologies to understand how aberrant cell signaling contributes to prostate tumor initiation and progression. The specific aims are to characterize the structural domain of FRS2? that are important for mediating FGFR signals; to characterize the role of FRS2 in prostatic development and tissue homeostasis; and to investigate how aberrant signals mediated by FRS2? contribute to prostatic tumorigenesis and tumor progression. The objective is to understand how FGFR elicits receptor specific signals at the substrate level and the roles of FRS2?-mediated signals in prostatic development, tissue homeostasis, and tumorigenesis. Understanding the role of FGFR signals in prostatic development and tumorigenesis will shed new light on designing new strategies for prevention and interception of prostate cancer initiation and progression in the future. Animal models developed in the project will provide a useful tool not only for further studying FGFR signals in prostate cancer initiation and progression, but also for assessing the role of nutrition and active dietary components on prevention, intervention, and interruption on prostate tumor progression.